Question of the Week

Can we mix human and spider DNA?

Sun, 2nd Dec 2012

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Question

Enrique asked:

If we put the DNA of spider into human what will happen?

Answer

We'll have the answer on the 2nd December Naked Scientists Show.  Until then, what do you think?

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It really depends on how the genes are spliced. Done randomly probably nothing would happen. Some time ago the genes responsible for making eyes in mice was spliced into a fly. The result was a perfectly normal fly eye. Even though the coding was for making a much more complex mammal eye, the genes still made an eye that the bug would use!
The chance of making a crime fighter would be very small. A human with the ability to spin spider silk would not have it coming out of his writs. More likely it would be in his urine, even then it would just be the proteins to MAKE spider silk rather than the silk itself, so even running around with parts of his body out that are normally covered in polite society it would not help.
Gaining the ability to climb walls is also unlikely. Spiders are really light compared to humans. The things they use to climb walls would not work for something as heavy as a person. krool1969, Tue, 27th Nov 2012

spider   pig    goat ... http://www.bbc.co.uk/news/science-environment-16554357 RD, Tue, 27th Nov 2012

DNA Compatibility: With few exceptions, a single DNA sequence will code for the same protein sequence, from humans to yeast.
Many proteins have "cousins" in other species, from humans to flies, so introducing a second version of the same protein is likely to cause development confusion.

DNA Delivery:When a spider bites, it injects a range of toxins to kill the target.
What is required is more akin to a retrovirus which injects a genetic sequence into a cell, which is then incorporated into the DNA of the target cell (rather than immediately killing the cell, like most viruses).
Ideally, it should be consistently delivered into a section of the genome which will not break some normal cell function, or cause cancer.
However, there is a large size difference between the size of the genetic payload a virus could deliver, and the size of an insect/spider's DNA (http://en.wikipedia.org/wiki/Genome#Genome_size). However, a virus could be used to deliver one or a small number of genes.

DNA Regulation:The new genes must be turned on in just the correct cells, and all of the normal functions of those cells must be disabled. This means turning on silk production in just the wrist region (for example). There is a web of epigenetic controls within a cell, and a chain of enzymes needed to process the proteins, all of which must be enabled in the right cells.

DNA-Directed Organs: At the lowest level, the silk protein monomer is fairly simple, but to generate a fiber with the right mechanical properties requires polymerisation under the right conditions and admixture of additional compounds, formed in a complex organ with many specialised cell types, orchestrated under control of the nervous system (http://en.wikipedia.org/wiki/Spider_silk#Silk_gland). Transposing the gene for spider silk into a silkworm was more successful than into goats, since the silkworm already has the organ structure for processing the silk monomer into a fiber.

Connecting the Organs: Unlike insects, spiders have up to 5 different types of silk for different purposes, including the structural framework of a web, and tying up prey. Each type has specific mechanical and chemical properties with a different amorphous/crystalline microstructure, produced in different silk glands. Producing silk is energetically demanding, so the blood supply would need to be redirected to support it. Some spiders eat their own webs to recycle the raw materials - making this appetising would require additional changes to the mammalian digestive system. The silk is produced and stored in large sacs, ready for use. So probably the wrist and forearm would not be the best location for Spiderman's silk glands.

DNA Inheritability: Adding one protein to the genome has been shown to be inheritable in goats and silkworms. However, if the DNA for the entire silk production process were added to the mammalian genome, the extra DNA would probably distort the structure of the mammalian DNA, making it hard to inherit the entire silk production chain.

Aerodynamics of Spider Silk: None of this will let you shoot jets of silk to the top of the nearest skyscraper. Even spiders let their silk waft in the breeze until it makes contact with another object, at the start of their web construction. evan_au, Wed, 28th Nov 2012

I expect it would be possible to produce a transgenic human female that would lactate spider silk protein in her milk. I doubt however whether SpiderMan's trick of shooting web-making material across a room could be mastered by our transgenic SpiderMom. Rev_Skip, Thu, 29th Nov 2012

Then we really could say, 'what a tangled web we weave'.

It would cost us a fortune in shoes and specs!

If the spider were the infamous Black Widow, it might put condom manufacturers out of business. Don_1, Sat, 8th Dec 2012

if we ever suceed in combing human dna with spider dna i hope i'm still alive by then! liam beavis, Tue, 30th Jul 2013

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